Using underwater currents as an occupational enrichment method to improve the stress status in rainbow trout

This study investigated the effects of occupational enrichment, specifically underwater currents, on the stress status of rainbow trout (Oncorhynchus mykiss). A total of 540 fish were divided into three groups: control tanks without artificial currents (CO), tanks with randomly fired underwater currents (RFC), and tanks with continuous current throughout the day (CT). After 30 days, half of the fish in each group underwent a 5-day pre-slaughter fasting (5D), while the others were fed until the day before slaughter (0D). Fish in the RFC group exhibited lower levels of plasma cortisol and acetylcholinesterase enzyme activity in hypothalamus and optic tract than other groups, suggesting an improved stress status. RFC group also showed higher levels of non-esterified fatty acids (NEFA) in 5D fish and higher liver glycogen stores, suggesting improved energy reserves. In comparison, the CT group had higher LDH levels, possibly due to their increased swimming activity. The CO group had significantly lower NEFA levels at 5D compared to the RFC group, suggesting lower energy reserves. The RFC fish had darker and yellow-reddish skin and liver color, suggesting an improved stress status and lower lipid reserves, respectively. Overall, although a significant stress response was not observed in fasted individuals, possibly due to the relatively short fasting period, the study suggests that providing occupational enrichment using randomly fired underwater currents for 1 month helped to improve stress status in rainbow trout, indicating that occupational enrichment during the grow-out phase can positively impact the welfare of rainbow trout during routine handling procedures.

Extending the Shelf Life of Atlantic Salmon (Salmo salar) with Sub-Chilled Storage and Modified Atmosphere Packaging in Recyclable Mono-Material Trays

This study investigated the effect of sub-chilling whole gutted salmon and sub-chilled storage at -1 °C in modified-atmosphere packaging in two recyclable mono-material trays (CPET, HDPE). Quality parameters were measured, including water-holding properties, salt content, color, texture, lipid oxidation, and sensory and microbiological shelf life. The oxygen transmission rate was measured for the packages. Compared to traditional fish storage on ice, sub-chilling gave a 0.4% weight gain, better water-holding capacity, and higher salt content. The sub-chilled fish gave a significantly better sensory quality and microbiological shelf life of up to 49 days. Photobacterium was the dominating bacteria during storage. Salmon packaged in CPET trays had a higher drip loss than HDPE trays, but a lower rate of lipid oxidation (1-penten-3-ol). Our results showed the feasibility of significantly extending shelf life with sub-chilling, removing the need for ice. Moreover, using recyclable trays for packaging contributes to a circular economy without compromising food quality.

Substituting Fish Meal with Tubiechong (Eupolyphaga sinensis) By-Product in the Diets of Largemouth Bass (Micropterus salmoides): Effects on Growth, Meat Quality, and Liver Health

A feeding trial was conducted to evaluate the effect of replacing 0% (control), 10% (T10), 20% (T20), 30% (T30), and 40% (T40) fish meal with a Tubiechong (Eupolyphaga sinensis) by-product in largemouth bass (Micropterus salmoides). Triplicate groups of 30 fish (5.36 ± 0.01 g) were fed two times daily to apparent satiation for 60 days. The experimental results showed that the Tubiechong by-product could improve the growth performance of largemouth bass by increasing the FBW, WGR, and SGR until the replacement ratio was 40%. The quadratic regression analysis showed that the proportion of the Tubiechong by-product was 20.79% and 20.91%, respectively, when WGR and SGR were the best. Concurrently, the meat quality in the replacement groups was higher, specifically, the lightness and white values were higher, and the water loss rates were lower (P < 0.05) than that in the control group. Moreover, the changes of the activities of CAT and GSH in the liver and T-AOC and GSH in serum could reveal the antioxidant capacity improvement of fish by the Tubiechong by-product. In the study, the replacement groups had lower T-CHO and HDL-C in serum (P < 0.05), indicating that the Tubiechong by-product had an active role in improving blood lipid and regulating lipid metabolism. Simultaneously, the replacement groups had a normal structure with central hepatocytes' nuclei and deviated from the center partly, while most of the hepatocytes were swollen in the control group with nuclear degeneration. The results showed that the Tubiechong by-product had a positive effect on the liver health of fish. Conclusively, the present study indicated that the partial dietary replacement of fish meal using the Tubiechong by-product (for up to 40% replacement level) in the diet of largemouth bass not only caused no adverse effects on fish health but also improved the growth performance, meat quality, antioxidant capacity, and hepatic health and is conducive to supplying nutritious, high-quality, and healthy aquatic products.

A novel hybrid system for automatic detection of fish quality from eye and gill color characteristics using transfer learning technique

Fish remains popular among the body's most essential nutrients, as it contains protein and polyunsaturated fatty acids. It is extremely important to choose the fish consumption according to the season and the freshness of the fish to be purchased. It is very difficult to distinguish between non-fresh fish and fresh fish mixed in the fish stalls. In addition to traditional methods used to determine meat freshness, significant success has been achieved in studies on fresh fish detection with artificial intelligence techniques. In this study, two different types of fish (anchovy and horse mackerel) used to determine fish freshness with convolutional neural networks, one of the artificial intelligence techniques. The images of fresh fish were taken, images of non-fresh fish were taken and two new datasets (Dataset1: Anchovy, Dataset2: Horse mackerel) were created. A novel hybrid model structure has been proposed to determine fish freshness using fish eye and gill regions on these two datasets. In the proposed model, Yolo-v5 and Inception-ResNet-v2 and Xception model structures are used through transfer learning. Whether the fish is fresh in both of the Yolo-v5 + Inception-ResNet-v2 (Dataset1: 97.67%, Dataset2: 96.0%) and Yolo-v5 + Xception (Dataset1: 88.00%, Dataset2: 94.67%) hybrid models created using these model structures has been successfully detected. Thanks to the model we have proposed, it will make an important contribution to the studies that will be conducted in the freshness studies of fish using different storage days and the estimation of fish size.

Assessment of quality deviation of pork and salmon due to temperature fluctuations during superchilling

Superchilling is an emerging technology for meat preservation; however, the temperature changes during the process have been commonly ignored. Thus, the effects of temperature fluctuations on meat quality during superchilling are yet to be evaluated. In our study, pork loins and salmon fillets were stored for several days (0, 8, 15, 23, and 30 d) under different temperature fluctuations based on -3.5 ℃ as the target temperature. The results showed that after 15 d of superchilling storage, the values of total volatile basic nitrogen, total viable count, and lipid oxidation were significantly (P<0.05) altered in the ±2.0 ℃ fluctuation group compared with the constant temperature group. On the contrary, there was no significant difference in these parameters between the ±1.0 ℃ fluctuation group and the constant temperature group after 30 d of storage. In addition, irregular temperature changes significantly accelerated the modulation of various indicators. In brief, temperature fluctuations and irregular temperature changes accelerated the destruction of muscle structural integrity, increased the water loss, gradually widened the water loss channels, and thereby reduced the edibility by accelerating the spoilage of meat.

Effect of edible coating and modified atmosphere packaging on the microbiological and physicochemical stability of retail maki sushi

The effect of pH, packaging atmosphere (100% air, 40%, or 70% CO₂ balanced with N₂ ), and an edible chitosan coating was tested on the retail maki Sushi's microbiological and physiochemical stability. In two experiments, maki sushi was studied using sushi rice with an initial pH of 4.2 ± 0.05 and 4.8 ± 0.05. In the first experiment (lower pH), no apparent effect of neither modified atmosphere packaging (MAP) nor coating on bacterial growth was observed. However, raising the pH showed an apparent effect of low-CO₂ MAP and chitosan coating (p < 0.05). Both MAP and coating partly affected the maki sushi cross-section's visual perception, but no significant adverse effects were observed. An important observation was the improved stability of the pink salmon color in chitosan-coated maki sushi stored in low-CO₂ MAP compared to other groups. It is concluded that storage of Maki sushi at 4°C gives acceptable microbial stability and appropriate quality. However, an edible chitosan coating, especially in combination with low-CO₂ MAP, increases the microbiological stability and preserves the colorimetric properties of maki sushi stored at 8°C. Notably, this combination could work as a safety measure against temperature abuse in the food cold chain. PRACTICAL APPLICATION: Using an edible coating with active packaging can improve retail maki sushi's temperature tolerance and preserve its colorimetric properties. It is a fast and cost-effective technology with a substantial industrial potential easy to implement.

Undesirable discoloration in edible fish muscle: Impact of indigenous pigments, chemical reactions, processing, and its prevention

Fish is rich in proteins and lipids, especially those containing polyunsaturated fatty acids, which made them vulnerable to chemical or microbial changes associated with quality loss. Meat color is one of vital criteria indicating the freshness, quality, and acceptability of the meat. Color of meat is governed by the presence of various pigments such as hemoglobin, myoglobin (Mb), and so on. Mb, particularly oxy-form, is responsible for the bright red color of fish muscle, especially tuna, and dark fleshed fish, while astaxanthin (AXT) directly determines the color of salmonids muscle. Microbial spoilage and chemical changes such as oxidation of lipid/proteins result in the autoxidation of Mb or fading of AXT, leading to undesirable color with lower acceptability. The discoloration has been affected by chemical composition, post-harvesting handling or storage, processing, cooking, and so on . To tackle discoloration of fish meat, vacuum or modified atmospheric packaging, low- or ultralow-temperature storage, uses of artificial and natural additives have been employed. This review article provides information regarding the factors affecting color and other quality aspects of fish muscle. Moreover, promising methodologies used to control discoloration are also focused.

Effect of handling and crowding on the susceptibility of Atlantic salmon (Salmo salar L.) to Lepeophtheirus salmonis (Krøyer) copepodids

Lepeophtheirus salmonis is an ectoparasite causing economic concerns in Atlantic salmon farming. Salmon lice infestation management methods can be stressful and impact fish welfare. This work investigated the stress effect on the attachment of L. salmonis copepodids to Atlantic salmon through two approaches: (a) handling by netting and air exposure (acute stress), and (b) crowding with restricted surface access in a tank (chronic stress). In the first experiment, we compared the number of attached L. salmonis and cortisol levels between a group of handled salmon and a control group. In the second experiment, a group of densely packed salmon was compared to a control group based on the number of attached copepodids, cortisol levels and neutrophil:lymphocyte ratios. Handled salmon showed significantly higher plasma cortisol levels (p < .001) and more attached copepodids (p = .01) than control salmon. Conversely, the cortisol level and number of attached copepodids were not significantly different between the densely packed and control salmon (p > .05). The neutrophil:lymphocyte ratio was significantly higher (p = .0014) in the densely packed salmon than in the control salmon. Handling salmon increased their risk of infestation by L. salmonis. This has implications for reinfestation rates following delousing treatments in commercial salmon aquaculture, which often involve crowding and handling salmon.

Post-mortem quality changes of common carp (Cyprinus carpio) during chilled storage from two culture systems

BACKGROUND

Omega-3 common carp (OCC) raised by patented culture systems have higher level of n-3 fatty acids and n-3/n-6 ratio than normal common carps (NCCs) from traditional culture system. Whether the patented farming system and modified fatty acid profile will influence OCC storage stability is unclear. This study aimed to expose the differences of post-mortem quality changes between NCC and OCC.

RESULTS

NCC and OCC have similar rigor mortis patterns, only a higher level of lactic acid was observed in NCC after 96 h. Adenosine triphosphate (ATP) related compounds had no major differences, but slightly higher inosine monophosphate in OCC was found at 36 h. The K-value, Ki-value and Hx-index demonstrated high cohesiveness (Pearsons two-tailed, r = 0.968-0.984, P < 0.05) during storage, with statistically comparable (P > 0.05) temporal progress of change in NCC and OCC. The indices were lower in OCC than in NCC. Attenuation of myosin heavy chain in OCC was not as distinct as in NCC, coincided with its higher salt-soluble protein level at 144 h. Before 96 h, thiobarbituric acid value (TBA), total viable count (TVC), cooking loss (CL), drip loss (DL), and hardness in NCC and OCC were similar. However, at 144 h, higher TBA, TVC, CL and DL while lower hardness in NCC than in OCC were observed. Principle component analysis showed good separation of NCC and OCC in biplot at 0 and 144 h.

CONCLUSION

Patented culture system has a slightly positive influence on post-mortem quality of common carp. It can be used for producing OCC without compromising storage stability. © 2020 Society of Chemical Industry.

Understanding the Determination of Meat Quality Using Biochemical Characteristics of the Muscle: Stress at Slaughter and Other Missing Keys

Despite increasingly detailed knowledge of the biochemical processes involved in the determination of meat quality traits, robust models, using biochemical characteristics of the muscle to predict future meat quality, lack. The neglecting of various aspects of the model paradigm may explain this. First, preslaughter stress has a major impact on meat quality and varies according to slaughter context and individuals. Yet, it is rarely taken into account in meat quality models. Second, phenotypic similarity does not imply similarity in the underlying biological causes, and several models may be needed to explain a given phenotype. Finally, the implications of the complexity of biological systems are discussed: a homeostatic equilibrium can be reached in countless ways, involving thousands of interacting processes and molecules at different levels of the organism, changing over time and differing between animals. Consequently, even a robust model may explain a significant part, but not all of the variability between individuals.

A comparative study of Atlantic salmon chilled in refrigerated seawater versus on ice: from whole fish to cold-smoked fillets

Water and salt uptake, and water holding capacity (WHC) of whole gutted Atlantic salmon superchilled at sub-zero temperatures in refrigerated seawater (RSW) were compared to traditional ice storage. Following the entire value chain, the whole salmon was further processed, and fillets were either chilled on ice or dry salted and cold-smoked. Changes in quality parameters including colour, texture, enzyme activity and microbial counts were also analyzed for 3 weeks. Our results showed that when fish were removed from the RSW tank after 4 days and further chilled for 3 days, an overall weight gain of 0.7%, salt uptake of 0.3% and higher WHC were observed. In contrast, ice-stored fish had a total weight loss of 1% and steady salt uptake of 0.1%. After filleting, raw fillets from whole fish initially immersed in RSW had better gaping occurrence, softer texture, lower cathepsin B + L activity but higher microbiological growth. Otherwise, there were no differences in drip loss nor colour (L*a*b*) on both raw and smoked fillets from RSW and iced fish. Storage duration significantly affected quality parameters including drip loss, colour, texture, enzyme activity and microbial counts in raw fillets and drip loss, WHC, redness and yellowness in smoked fillets.

Changes on the Development of Rigor Mortis in Cultured Tilapia (Oreochromis niloticus) Fed with a Mixture of Plant Proteins

In recent years it has been pointed out that the feed of farmed fish has an effect on the quality of the final product. Therefore, this study evaluated the effect of fishmeal (FM) replacement by a mixture of plant protein (MPP) on the development of rigor mortis of tilapia (Oreochromis niloticus). One hundred and twenty fish at an initial average weight of 123 ± 6.3 g were fed with three extruded isonitrogenous and isolipidic 6.2% crude lipids experimental diets, in which FM were replaced by 0% (D0), 50% (D50), and 100% (D100) of MPP (soybean meal, corn meal, wheat meal, and sorghum meal). A reference diet (DC) containing FM as the main protein source was used as a control. The fish were divided into triplicate groups per dietary treatment. The experiment was conducted in a tank system at 26.8°C water temperature for 67 days. The chemical composition of experimental diets and muscle were determined. The glycogen, adenosine 5′-triphosphate (ATP) and related compounds, pH, shear force, and rigor index (RI%) were monitored during storage on ice for 48 h. The results indicated that FM replacement affected (p≤0.05) the muscle composition, where the fish fed with D100 presented the higher content of lipids and ash. Fish fed with D0 and DC presented a more pronounced onset of rigor mortis and also showed a higher IR%, a lower content of glycogen, ATP, adenosine 5′-diphosphate (ADP), adenosine 5′-monophosphate (AMP), pH, and shear force. The changes in chemical composition of muscle and other parameters evaluated indicated that FM replacement increases energy reserves (glycogen, ATP, ADP, and AMP) which delayed the onset of rigor mortis, as well as a lower pH and shear force in the muscle of tilapia. Therefore, the substitution of FM by MPP could contribute to delaying the onset of rigor mortis and with this, the quality and shelf life of tilapia could be increased.

Physiological and flesh quality consequences of pre-mortem crowding stress in Atlantic mackerel (Scomber scombrus)

In commercial wild capture pelagic fisheries it is common practice to crowd catches to high densities to allow efficient pumping onboard. Crowding during the final stages of purse seine capture for small pelagic species often results in intense and sustained behavioural escape responses. Such a response may trigger a shift in energy production from aerobic to anaerobic pathways and result in metabolic acid accumulation and exhaustion of intracellular reserves of ATP. Where there is insufficient time or opportunity to recover to physiological equilibrium before death, pre-mortem stress may be an important determinant of fillet quality, as has been shown for a variety of farmed fish species. However, there is currently a lack of knowledge related to the flesh quality implications of capture stress for wild captured species in European waters. Here we show that crowding results in a physiological stress response that has consequences for flesh quality in the wild captured species Atlantic mackerel (Scomber scombrus). Using small schools in tanks and aquaculture net pens in three separate experiments, we found crowding results in physiological changes in mackerel consistent with an acute stress response and anaerobic metabolism. Consequently, we found crowded fish had more acidic pre- and post-mortem muscle pH as well as indications of faster onset and strength of rigor mortis and increased cathepsin B & L activity. We examined fillet flesh quality after two and seven days of ice storage and found reduced green colouration, increased gaping (separation of muscle myotomes) and reduced textural firmness associated with fish which had been crowded. However, the effects on quality were dependant on experiment and/or storage time. These results indicate the potential of crowding capture stress to influence the flesh quality of an economically important species and may have important implications for the wild capture pelagic fishing industry.

QTL Mapping for Red Blotches in Malaysia Red Tilapia (Oreochromis spp.)

Body color is an interesting economic trait in fish. Red tilapia with red blotches may decrease its commercial values. Conventional selection of pure red color lines is a time-consuming and labor-intensive process. To accelerate selection of pure lines through marker-assisted selection, in this study, double-digest restriction site-associated DNA sequencing (ddRAD-seq) technology was applied to genotype a full-sib mapping family of Malaysia red tilapia (Oreochromis spp.) (N = 192). Genome-wide significant quantitative trait locus (QTL)-controlling red blotches were mapped onto two chromosomes (chrLG5 and chrLG15) explaining 9.7% and 8.2% of phenotypic variances by a genome-wide association study (GWAS) and linkage-based QTL mapping. Six SNPs from the chromosome chrLG5 (four), chrLG15 (one), and unplaced supercontig GL831288-1 (one) were significantly associated to the red blotch trait in GWAS analysis. We developed nine microsatellite markers and validated significant correlations between genotypes and blotch data (p < 0.05). Our study laid a foundation for exploring a genetic mechanism of body colors and carrying out genetic improvement for color quality in tilapia.

Air Exposure in Catshark (Scyliorhinus canicula) Modify Muscle Texture Properties: A Pilot Study

Sharks are captured by tons for human consumption. Improving the quality of their meat will produce fillets that may have a higher economic value in the market, and thus be beneficial for the management of this fishery. In other animal species destined for human consumption, a negative relationship between pre-slaughtering stress and meat quality has been demonstrated. By studying the commercial small-spotted catshark (Scyliorhinus canicula), this work aimed at linking pre-slaughter handling of captured sharks and muscle fillets quality. An experimental group of adult and subadult living catsharks captured by hand and exposed to air (for 18 min, which is the minimum time this species is exposed to air in the fishing deck during fisheries procedures), and an undisturbed group, were evaluated. After air exposure, catsharks returned to water for recovery. Muscle lactate and water content were quantified after acute exposure (for 18 min), 5 h and 24 h. This challenge elicited stress responses in the muscle such as increased lactate levels and immediate dehydration, followed by recovery of lactate levels and overhydration. Muscle consistency, a relevant variable describing quality of seafood according to its ability to be swallowed by the consumer, paralleled muscle water content changes. The results indicated for the first time that handling alive sharks exposed to air results in muscle fillets with different texture properties. Whether these changes in muscle texture induce higher quality fillets has yet to be proven. Our recommendation is to minimize time of air exposure experienced by sharks when captured, including fast slaughtering instead of leaving them to die by asphyxia, as current on-board procedures.

Comparative Performance Analysis of Support Vector Machine, Random Forest, Logistic Regression and k-Nearest Neighbours in Rainbow Trout (Oncorhynchus Mykiss) Classification Using Image-Based Features

The main aim of this study was to develop a new objective method for evaluating the impacts of different diets on the live fish skin using image-based features. In total, one-hundred and sixty rainbow trout (Oncorhynchus mykiss) were fed either a fish-meal based diet (80 fish) or a 100% plant-based diet (80 fish) and photographed using consumer-grade digital camera. Twenty-three colour features and four texture features were extracted. Four different classification methods were used to evaluate fish diets including Random forest (RF), Support vector machine (SVM), Logistic regression (LR) and k-Nearest neighbours (k-NN). The SVM with radial based kernel provided the best classifier with correct classification rate (CCR) of 82% and Kappa coefficient of 0.65. Although the both LR and RF methods were less accurate than SVM, they achieved good classification with CCR 75% and 70% respectively. The k-NN was the least accurate (40%) classification model. Overall, it can be concluded that consumer-grade digital cameras could be employed as the fast, accurate and non-invasive sensor for classifying rainbow trout based on their diets. Furthermore, these was a close association between image-based features and fish diet received during cultivation. These procedures can be used as non-invasive, accurate and precise approaches for monitoring fish status during the cultivation by evaluating diet's effects on fish skin.

Differential abundance of muscle proteome in cultured channel catfish (Ictalurus punctatus) subjected to ante-mortem stressors and its impact on fillet quality

The effects of environmental and handling stress during catfish (Ictalurus punctatus) aquaculture were evaluated to identify the biochemical alterations they induce in the muscle proteome and their impacts on fillet quality. Temperature (25°C and 33°C) and oxygen (~2.5mg/L [L] and >5mg/L [H]) were manipulated followed by sequential socking (S) and transport (T) stress to evaluate changes in quality when fish were subjected to handling (25-H-ST; temperature-oxygen-handling), oxygen stress (25-L-ST), temperature stress (33-H-ST) and severe stress (33-L-ST). Instrumental color and texture of fillets were evaluated, and muscle proteome profile was analyzed. Fillet redness, yellowness and chroma decreased, and hue angle increased in all treatments except temperature stress (33-H-ST). Alterations in texture compared to controls were observed when oxygen levels were held high. In general, changes in the abundance of structural proteins and those involved in protein regulation and energy metabolism were identified. Rearing under hypoxic conditions demonstrated a shift in metabolism to ketogenic pathways and a suppression of the stress-induced changes as the severity of the stress increased. Increased proteolytic activity observed through the down-regulation of various structural proteins could be responsible for the alterations in color and texture.

Effect of a Phenolic Extract from Olive Vegetation Water on Fresh Salmon Steak Quality during Storage

This study aimed to evaluate the antioxidant and antimicrobial effects of a phenolic extract from olive vegetation water on fresh salmon steaks stored at 4°C under modified atmosphere. Twenty-four salmon steaks were respectively immersed in solutions of the diluted phenolic extract at 1.5 g/L (A), 3 g/L (B), and water only as a control (CTR), packaged within a protective atmosphere (70% carbon dioxide, 25% nitrogen and 5% oxygen) and then stored at 4°C. After 2 h, and 3 and 6 days of storage, the fish samples were analysed for the total viable count, Enterobacteriaceae count, pH, colour (CIE L*a*b* colour system), phenolic composition, atocopherol content, antioxidant activity by 2,2- diphenyl- 1-picrylhydrazyl (DPPH˙) assay, and thiobarbituric reactive substances (TBARS). A 3 g/L phenolic extract contributed positively to the hygienic quality of the salmon by reducing the microbial growth during storage. The treated samples were slightly yellower than the CTR but only at the beginning of storage. The flesh contained 6.2% of the total polyphenols present in the initial solutions, with various percentages of the single fractions. After 6 days storage, the α- tocopherol content in the CTR and A samples was statistically lower than the B group that also showed the lowest DPPH˙ and TBARS values. In conclusion, the phenolic extract increased the microbiological quality and antioxidant concentration and decreased the lipid oxidation of salmon steaks during storage at 4°C under modified atmosphere.

Recent advances in methods and techniques for freshness quality determination and evaluation of fish and fish fillets: a review

The freshness quality of fish plays an important role in human health and the acceptance of consumers as well as in international fishery trade. Recently, with food safety becoming a critical issue of great concern in the world, determination and evaluation of fish freshness is much more significant in research and development. This review renovates and concentrates recent advances of evaluating methods for fish freshness as affected by preharvest and postharvest factors and highlights the determination methods for fish freshness including sensory evaluation, microbial inspection, chemical measurements of moisture content, volatile compounds, protein changes, lipid oxidation, and adenosine triphosphate (ATP) decomposition (K value), physical measurements, and foreign material contamination detection. Moreover, the advantages and disadvantages of these methods and techniques are compared and discussed and some viewpoints about the current work and future trends are also presented.

Muscle temperature at the point of filleting—Subsequent effect on storage quality of prerigor filleted raw- and cold-smoked Atlantic salmon

The impact of increased muscle temperature at the point of filleting on fillet quality of raw- and cold-smoked Atlantic salmon was investigated. Commercially reared fish (5.65 kg, Kf: 1.23, pH: 7.29, muscle temperature: 6.68 ℃) were killed and immediately tempered in three different containers. Muscle temperatures after filleting (<3 h postmortem) of the three groups were 2.08 ℃ (hereafter named T-2); 9.07 ℃ (hereafter named T-9), and 14.09 ℃ (hereafter named T-14), respectively. The pH after filleting was significantly low for T-14 (6.93) followed by T-9 (7.06) and T-2 (7.22). Raised temperature at point of filleting was found to significantly alter development of rigor mortis, which subsequently affected muscle pH and the reflective properties of the fillet surface during 14 days' ice storage. Of cold-smoked fillets, however, a more distinct effect of raised temperature was observed on visual perception resulting in lighter and more yellowish cold-smoked fillets after 14 days' storage. In addition, raised temperature also affects the development of muscle pH in cold-smoked fillets during refrigerated storage. No effects of raised muscle temperature were found regarding drip loss, water-holding capacity, or fillet firmness either for raw- or cold-smoked fillets throughout the storage period.